The Sundarban World Heritage Mangrove Forest demands immediate conservation

Tiger attacks are one of the rarer fieldwork safety concerns here at the Institute, but they were a serious consideration for PhD student Swapan Kumar Sarker. Swapan’s research focuses on spatial analysis of biodiversity in the Bangladeshi Sundarban, the worlds largest continuous mangrove forest and a UNESCO World Heritage Site.

Already an accomplished researcher, with a proven track record of successful field research in the challenging mangrove environment, Swapan joined the institute in 2013 to pursue his doctoral studies under the supervision of Prof. Jason Matthiopoulos and Dr. Richard Reeve. Here he shares his passion for, and experiences in, this fascinating mangrove ecosystem.

(Excitingly a short documentary based on Swapan’s research has also been made, you can find it at the bottom of this post!)

Tidally inundated forest floor in the Bangladesh Sundarbans
Tidally inundated forest floor in the Bangladesh Sundarban © Swapan Kumar Sarker

The Sundarban World Heritage Mangrove Forest demands immediate conservation

Mangroves are trees and shrubs that grow in the interface between land and sea. They are well equipped to survive under the extreme environmental conditions of their tropical and subtropical coastal habitats: high salinity levels, regular flooding, poor soil conditions, and high temperatures. These conditions would have a devastating effect on most plant life, so how do mangroves survive?

One of the biggest challenges for mangrove species is obtaining enough water. Salt can have a lethal effect on plant life, so mangroves must spend much of their valuable time and energy filtering sea water and storing it as a freshwater reservoir. This helps them survive during seasons of increased stress.

As well as securing their next drink, mangroves need to put more care into ensuring the next generation than most temperate plants. The harsh coastal environment can be a dangerous place for baby mangroves! To give them the best possible start in life, seeds germinate whilst the fruit is still attached to the mother tree. By remaining close the sapling has time to develop in a more friendly environment.

These are just two of the most important strategies mangroves have developed for survival. Although there are only 60 species, they have evolved to be strong and resilient, making them highly successful. However, mangroves are not immune to human activities. Like much of the natural world they are coming increasingly under threat.

Is the ‘Mangrove Biome’ approaching extinction?

Already over 50% of the world’s mangroves have been destroyed, a staggering 35% of which has occurred in the past 20 years. Their destruction is due to coastal development projects, shrimp cultivation, overexploitation, altered hydrology (the movement of terrestrial water), and rising sea-levels. At present the IUCN Red List reports a declining population trend in almost all mangrove species: 16% of all mangrove plants are critically endangered, endangered, or vulnerable, and 10% are near threatened. This also means that around 40% of all mangrove-dependent animals are also at risk of extinction.

If nothing changes, it has been suggested that the whole mangrove biome could disappear within the next 100 years. Of the 120 countries in which they are found, mangroves are critically endangered or at elevated risk of extinction in 26 of them. This includes Bangladesh, the focus of my research and home to the largest continuous mangrove forest in the world—the Sundarban.

The Sundarban – a stressed ecosystem

The Sundarban covers large swathes of both Bangladesh and India, and is more than just mangrove. The Bangladeshi Sundarban (6,017 km2) is a highly diverse, species rich ecosystem containing more than 300 plant, 120 fish, 35 reptile, 300 bird, and 32 mammal species. It is also the last remaining habitat of the Royal Bengal tiger.

The livelihoods of over 3 million people, mainly fishermen and honey collectors, depend on the Sundarban. However, historical human pressures such as overexploitation, dam construction, shrimp and salt farming, and regular oil spills have heavily degraded the ecosystem. The Bangladeshi coastal ecosystem is also considered to be one of the world’s most vulnerable ecosystems to climate change. In the last century, sea levels have risen by 5.93 mm/year along the Bangladeshi coast, which is considerably higher than the global average of 1.0–2.0 mm/year. If this continues, there will be serious consequences in terms of biodiversity.

Mangrove forest populations in the Sundarban have drastically declined over the last few decades. This has resulted in several Sundarban species being elevated in terms of their extinction risk: six species of mangrove, two amphibians, 14 reptiles, 25 birds, and five mammal species. Three mangrove species (of the genus Bruguiera) and at least six mammal species (wild buffalo, Javan rhinoceros, one-horned rhinoceros, swamp deer, hog deer, and gaur) have disappeared completely. As a result the situation is now a national priority.

Saving the Sundarban is saving Bangladesh

The Bangladeshi are proud of the Sundarban. This iconic landscape is a sanctuary for many endangered species, provides a sustainable livelihood for its people, and is one of the most biodiverse regions in the world. If this weren’t enough, the Sundarban provides protection for the Bangladeshi people, saving lives by acting as a bio-shield against cyclones and tropical storms. Now the Sundarban needs our protection.

Prawn larvae fishing in the Sundarbans
The Sundarban supports livelihoods: Prawn larvae fishing © Swapan Kumar Sarker

In 2014, a massive oil tanker collided with a cargo vessel in the Sundarban, spilling thousands of gallons of crude oil—the effects were devastating, but the situation gets bleaker still. The Bangladeshi government have decided to build a large coal-fired power plant in the neighbouring district of Bagerhat. Environmentalists and civil society groups are protesting this plan, worried that the proposed Rampal Power Plant might pollute the Sundarban irreparably. The government is now under constant public pressure to take every step necessary to conserve the biodiversity of this unique and globally important ecosystem.

OK, then what we are doing?

My research focuses specifically on the Sundarban mangroves. I believe effective conservation (now and in the future) of mangrove forests requires the accurate collection and assessment of information: where are the threatened mangroves located? How many regions are threatened? Which environmental conditions do they prefer? Where are the unique habitats (biodiversity hotspots)? Has uniqueness decreased (or hopefully, increased) over time? How does mangrove biodiversity respond to environmental stress and human pressure?

I am trying to answer these questions based on species and environmental data, which we collected from a permanent sample plot network (120 sites) of the Bangladesh Forest Department (BFD). So far I have only conducted the field research, but the inhabitants of the Bangladeshi Sundarban made this more difficult than you might suspect.

Fieldwork in Sundarban – you should be tiger friendly!

We (eight guys) had to make a Royal Bengal tiger friendly fieldwork plan (January – June 2014). There are about 106 tigers in the forest, and they won’t tolerate you if you invade their privacy, though you may make a perfect snack. Every year tigers kill 20 – 30 people in the area, and wound even more. This meant we had to be extremely careful whilst counting, marking, and tagging trees, and even more careful when collecting soil, leaf, and wood samples. A couple of times the tigers came very close—you can sense them if there’s a sudden bad smell and silence. We honoured it by firing shots in the air and leaving immediately.

Fieldwork team
The fieldwork team, with Swapan at the centre © Swapan Kumar Sarker

Working in the Sundarban means you must endure extreme heat, turbulent water, rainstorms, and salt water. Other difficulties include managing oneself in a small boat and caring for field assistants, who after two or three days may feel bored or concerned about the harsh environment. My experience is that any fieldwork in the mangroves is less about science, and more about managing people, risks, and uncertainties. It is important then that a researcher be crystal clear about who is going to do which job. Time matters everywhere, but in the mangroves, time matters more! Because the more time you stay in the forest, the more likely a tiger will attack.

Minimizing the gap between science and policy-makers

Bangladesh Forest Department (BFD) is the sole authority in the management and conservation of the Sundarban. The BFD was actively involved during the project planning and fieldwork phase of this work. Our project goals were designed and based on the present needs of the BFD, ultimately focused on aiding the conservation of mangrove forest. Our research outcomes will help the BDF develop much-needed management and conservation plans. Both we and the BFD believe this is a long term collaboration, which will help protect the diversity and majesty of the Sundarban mangroves.

“This is a documentary based on Sundarbans, its major flora and faunas and also about some of its people living on its resources and their life style. Which is created by ‘G Studio’, a Green Explore Society production.”


Read Swapan’s research papers bringing together some of this work:

How to cite this article: Sarker, S. K. et al. Are we failing to protect threatened mangroves in the Sundarbans world heritage ecosystem? Sci. Rep. 6, 21234; doi: 10.1038/srep21234 (2016).

Sarker, S. K. et al. Modelling spatial biodiversity in the world’s largest mangrove ecosystem—The Bangladesh Sundarbans: A baseline for conservation. Diversity and Distributions. 00:1–14 (2019).

Sarker S. K. et al. 1980s–2010s: The world’s largest mangrove ecosystem is becoming homogeneous. Biological Conservation. 236, 79-91 (2019).

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